The present invention described herein relates to the field of gaskets. More specifically, the invention relates to gaskets used to provide shielding from electromagnetic wave interference (EMI) and used to provide hermetic sealing. The invention especially relates to a gasket material used between graphite skin panels and aluminum structural components used in aircraft.
Gaskets to shield from EMI which are installed between graphite skin panels and aluminum frame components in aircraft are known. More specifically, such known gaskets are bonded to the aluminum frame components by using room temperature fluorosilicon compounds containing acetic acid.
Several problems arise from using the known EMI-shielding gaskets and the acetic-acid-containing bonding agent. First, severe corrosion, including pitting and exfoliation, of the aluminum frame components can take place, due primarily to the presence of the acetic acid. Second, since the bonding agent is nonconductive, electrical continuity is not provided between the graphite skin panels and the aluminum frame. This lack of electrical continuity permits charge separation and build up of electromotive force whereby corrosion due to differences in oxidation-reduction potential between the separated materials is accelerated. And, third, the hermetic sealing provided is somewhat limited.
In view of the above-described problems with the known EMI-shielding gaskets and the bonding agents used therewith between graphite skin panels and aluminum frame structures, it would be desirable to provide an EMI-shielding gasket that inhibits corrosion of the aluminum frame components, that provides electrical continuity between the graphite panels and the aluminum frame components thus affording EMI protection, and that provides an effective hermetic seal.
An important aspect of a suitable EMI shielding gasket is that exhibits a sufficient amount of resiliency to enable it to be compressed and expand as the parts between which it is installed move toward each other or move away from each other slightly.
With aircraft equipped with EMI shielding, at times degradation of the EMI shielding is observed. In such a case, the aircraft has to be partially disassembled to clean off residual gaskets from gasketted joints, and then new gaskets must be reinstalled. And as stated hereinabove, the new gaskets contain corrosion inducing agents such as acetic acid. Moreover, the process of disassembly, cleaning, installation of a new gasket, and reassembly is very time consuming and runs on the order of three days with certain aircraft. It would be desirable, therefore, to provide a more efficient way to repair EMI shielding gaskets whose EMI resistance has degraded in aircraft equipped with EMI shielding gaskets.